T-Pain Is On A Boat

Tuesday, December 3, 2024

Re: [electricboats] Complex design issues

"…..or am I way off? 100watts/12volts =8.33 amps x 4 =33.3 .......100watts/18volts= 5.5amps x 4= 22.2amps……"

You are way off.

You "add voltage in series" and "add amps in parallel".

So your 4x100watt 12 to18V panels get you 48 to 72 Volts at 5.5 to 8.33 Amps. Then times 2 (for your two strings in parallel) gives your solar array a max output of 72 Volts at 16.66 amps with a minimum of 0 Volts and 0 amps (like at night). 16.66 Amps is the max even though it would only be 16.66 at 48 Volts, it is still the max Amps. And the only reason to know the max amps is to size the wire from the panels to the controller.

So whatever controller you use needs to be able to handle this max Voltage output as the controllers input. So you could probably get by with a 100 Volt controller as your panel array is set up now.

On Solar controllers the listed Voltage is the max input but the Amps listed are the max output. Your Max output Amps is determined by max Watts of combined solar panel output divided by battery pack voltage. In your case 800W/48v=16.66A (a battery depleted all the way down to 40V would get you 20A). So a 20A output controller would work for you.

So it would seem that you need a 100v 20A solar controller. You must now make sure that the one you use has capability to output for 48V batteries (I have one 100V30A controller that will only charge 12V or 24V batteries, but its OK cause I have several 12V and a couple 24V battery packs).

It just so happens that Victron makes a 100V/20A@48V controller. I have a Victron 150V/35A@48V. I also have a BougeRV 150/40@48V and I am very happy with all my controllers, none of them have failed me yet.

Just realize that all the rated Watts, Volts, and Amps of any solar panels are THEORITICAL maximums. If you were to see an actual 100 Watts from a 100 Watt panel, you might be the first. I have some 440's that I have never seen more than around 375 Watts. And if the voltage drops on your panel, the amps will usually drop also because its from a lack of sun. So you will never see 8.33 Amps at12V or the full 5.5 Amps at 18V, but that's what you use to size the controller.

If the voltage from your solar panels drop below the minimum needed to charge it will simply stop charging.

A good solar controller will regulate the output voltage to whatever is best to charge the batteries connected to it, this is why usually you have to hook up the batteries to the controller first, so it can sense the voltage of the batteries it is trying to charge, but you will have to set the chemistry type and maybe the settings for your particular battery pack.

Any controller will use some of the voltage and/or amps from the solar panels for operation, so there will be some voltage drop across the controller. This is normal and at least one reason that actual voltage input needs to be more than planned voltage output. This is known as a voltage step-down converter. I don't know of any SOLAR battery charger/converters that will step up AND down. They might be out there somewhere, but I don't know of any, I have only ever seen solar step-down charger/converters. Now if you were charging a higher Voltage battery with a lower voltage battery, you could use a DC to D/C step-up converter, but those only go up, not up and down.

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Monday, December 2, 2024

Re: [electricboats] Complex design issues

I'm using Victron MPT 150/35 charge controllers on each of my 3 panels that are in series and it has no issue evening out the voltage. It has a rotary switch that lets you set the charge profile depending on the battery chemistry. I don't think it converts excess voltage to current (probably just regulates it down to the correct level) but it has never damaged the batteries during charging.

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Re: [electricboats] Complex design issues

Yes, I've been thinking about that, in that the panels are rated at 12 volts but on a sunny day, they roll out an average of 18 volts. That's the dilemma. With each panel putting out 18 volts, I'll have more voltage (and less amperage) with 22amps/hr vs 33.3amps if the panels are only putting out 12 volts each. The system would then be putting out 72 volts rather than the 48 volts to charge a bank of batteries. I agree that a charging rate above 48 volts.....up to 54, according to some sources, is desirable, to charge a 48 volt bank.

The answer to the dilemma is, as you mentioned, to probably get a 150 volt controller with a 20 (or more likely 40 amp) potential output. If the panels drop down to 12 or 13 volt output, there would be an increase in amperage, right? That could bring the amperage up to 33.3 amps and the controller would have to handle it.....or am I way off? 100watts/12volts =8.33 amps x 4 =33.3 .......100watts/18volts= 5.5amps x 4= 22.2amps. Question #2 is if the controller can handle the increased incoming voltage of say 72 volts and the batteries gobble up the outgoing 22.2 amps, how can we get that extra few volts to add to the 48 volts needed by the batteries to be effectively charged? Can the controller recognize that and feed the batteries 54 volts to charge? I have a Xantrex C60 model controller I use on the wind generator but it will only accept 12 or 24 volts up to 55 volts input but can regulate up to 60 amps. It isn't suited for this and I'll need another controller to do what you suggest. Any recommendations?

On Mon, Dec 2, 2024 at 7:30 PM gsxbearman via groups.io <gsxbearman=yahoo.com@groups.io> wrote:

" I have 8 100watt/12 volt panels ……"

I have seen some 100 Watt panels advertised as 12V, but most actually put out somewhere between 21 and 26 "open Volts" (just measured with a meter and not connected to anything). If there is no data plate on your panels that tells you the open voltage, then you need to measure it because it is important to size your controller.

For example if your cells actually put out 26 open volts, and you had 4 in series, then a 100 Volt controller wouldn't be big enough.

But here's the thing, if they only put out an actual 12V open volt, then 4 in a series would not be enough to charge a 48V battery pack, even a lead acid, you would need a minimum output of 51.8 to charge lead acid (and it would take a loooong time).

So if your 4 panel strings are capable of around 100V, then you probably gonna want a 150V 20A controller (20A because 800W/48v=16.66A).

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Re: [electricboats] Complex design issues

" I have 8 100watt/12 volt panels ……"

I have seen some 100 Watt panels advertised as 12V, but most actually put out somewhere between 21 and 26 "open Volts" (just measured with a meter and not connected to anything). If there is no data plate on your panels that tells you the open voltage, then you need to measure it because it is important to size your controller.

For example if your cells actually put out 26 open volts, and you had 4 in series, then a 100 Volt controller wouldn't be big enough.

But here's the thing, if they only put out an actual 12V open volt, then 4 in a series would not be enough to charge a 48V battery pack, even a lead acid, you would need a minimum output of 51.8 to charge lead acid (and it would take a loooong time).

So if your 4 panel strings are capable of around 100V, then you probably gonna want a 150V 20A controller (20A because 800W/48v=16.66A).

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Re: [electricboats] Complex design issues

"Do solar panel charge controllers work well with lithium batterys?"

Here is the age old "it depends" answer……

IF, your controller is capable of being set up for your battery/batteries/battery pack, AND it is set up correctly….THEN, YES they work great.

IF, you have an old controller that can not be set up for your specific type and size of batteries, THEN NO.

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Re: [electricboats] Complex design issues

NP Dale good luck with the set up. I'd recommend trying different locations/angles and measuring the output voltage/current to see what works best.

Other than the efficiency I find that using separate strings in series works pretty well. I usually put one set on my front deck and the other on the boom.

Most of my sailing is week night racing with some weekend day sailing so I'm only charging the batteries 7-8 times/summer. It usually takes around 5 days to bring it to a full charge from 60%.

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Re: [electricboats] When the ideal house voltage please stand up?

I think it wise to always have a separate 12V system for your instruments, running lights, and communications along with at least one stone age lead acid (or AGM) battery to power it with. And know that you can charge a 12V lead acid battery directly from a 100 watt solar panel in an emergency situation. You have to babysit the battery and disconnect the panel when the battery gets hot (or before).

This is a safety issue for when your 48V to 120 A/C inverter quits working (notice I didn't say IF I said WHEN, just remember. it is boat) but you will carry a spare inverter right? And you can change it out in 5-8 foot seas, in the dark, while raining, with no problems right? Because that's when things quit or get broken, the absolute worst time you can think of. But not to worry, your ole magnetic compass is right there by the wheel so you can see it, well if the wind hasn't blown your hat off so you can keep the rain out of you eyes.

Now with that being said, once you have this separate, almost bulletproof, navigation/communication system sorted, there is nothing wrong with using your traction batteries to power the rest of your "house". And /or using the traction batteries to charge the nav/comm battery with a DC to DC step-down.

So Aton listed 3 systems;

Propulsion

generator charging

and solar charging.

I would add;

the nav/comm system

and the shore power charging system.

Each separate system alone should be simple enough but adding them all together is more complicated.

But once connected, having them all separate means that they will be easier to troubleshoot when one system stops working in the conditions listed above.

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T-Pain Is On A Boat

Tuesday, December 3, 2024

Re: [electricboats] Complex design issues

Monday, December 2, 2024

Re: [electricboats] Complex design issues

Re: [electricboats] Complex design issues

Re: [electricboats] Complex design issues

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Re: [electricboats] When the ideal house voltage please stand up?

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